Alcohol fermentation is known from old in fermentation of alcohols such as Japanese sake, beer, wine, etc. In recent years, the alcohol fermentation has also been applied to preparation of energy alcohol as biofuel, as a substitute for petroleum.
In alcohol fermentation as biofuel, fermentation should efficiently be performed using inexpensive starchy raw materials from a standpoint of preparation of alcohol fuel and, survey of cheap raw materials of development and investigations on excellent various yeasts have been extensively made.
On the other hand, development has also been made from fermentation engineering, in which yeast cells are immobilized to prepare alcohol continuously and efficiently.
However, these techniques are all insufficient for improving fermentation efficiency to such an extent that they could achieve any economical effect. Under the actual situation, alcohol fermentation as biofuel still remains at the stage of research.
The present inventors previously began to work on physiologically active substances for plant, synthesized a variety of compounds and found that N-acyl lactam compounds were excellent as active substances (Japanese Patent Application Laid Open No. 61-246105). As a result of further investigations, they have found that 1-[2-(4-hydroxybenzoyl)ethanoyl]-2-piperidone of the present invention, which is a novel N-acyl lactam compound, shows an excellent fermentation promotive capacity and have accomplished the present invention, based on such a finding.